View Full Version : Can High Megapixel count = a decent zoom replacement?

11-14-2004, 12:37 AM
I'm doing some shopping for someone, since they don't know much about digital photography, and they wanted better than average zoom but they want the camera to be small too. Since I know that's not possible in 2004, I wanted to know what you all think of using a high megapixel count to ''make up'' for lack of telephoto power. In case I am being too vague, I have this example: A bird is 30 feet away and I take a picture of it zoomed in at 115mm on a standard 3x zoom. The bird is still too small in the picture, but if the shot were taken with a 7mp camera, would I be able to "zoom and crop" in post processing while maintaining decent quality in sharpness and detail? I'm not expecting it to replace a telephoto lens, but maybe it could work just well enough. What do you guys/gals think? I don't have a 7mp or 6mp camera on hand to try it out for myself, so any kind of help would be great.
Thanks a bunch! :)

11-14-2004, 02:28 AM
Yes and no.

While it's true that with a high quality high megapixel count camera with a lower focal length you can make suitable prints, you have to consider things like camera shake effect. The shorter the focal length the more pronounced the shake will be on far away objects once zoomed in. This is true with longer focal length zooms, but you tend to be able to see it less, because the relative shake has a finer distortion (a few pixel shift looks less significant on a 5 megapixel image vs a 2)

I've shot some birds @ 105 MM on my rebel and croped they made acceptable prints, but they'd of been better @ 300 mm


11-14-2004, 02:35 AM
In simple terms NO. It will not make up for a poor quality lens either, I have seen a post with the maths of why zoom (optical) is better when you consider Pixels v zoom but can not find it now.

11-14-2004, 05:49 AM
Yes it is true that having more megapixels can give you the equivalent of a bigger zoom, BUT optical zoom is MUCH more powerful than cropping with more megapixels.

For example, if you are using a 2mp camera with 2x zoom, then you'd need a 8mp camera with no zoom to be able to crop and have about the same quality image. Yes that is 4 times more mp for 2x more zoom.

Another example much more shocking. Say you have a 3mp camera with 10x zoom(like the S1 IS, 380mm) u wanted to know how many megapixels u needed to get a similar zooming capability with a 3x zoom camera(says 114mm), then you'd need at least 35megapixels. Yes 35!!!

So, as I said, yes more megapixels gives you "more zoom", but its very limited... A camera with maximal optical zooming capability of 114mm and 5mp(like the A95) would be able to have an effective zoom after cropping of 147mm and still retain the quality of a 3mp camera. Its a good feature, but as you can see it basicly makes a 3x zoom camera a 4x one.

11-14-2004, 12:28 PM
More or less, no. This method wouldn't really work - especially for prints. Perhaps for online viewing, and if it's quite an expensive 7/8MP ( low noise, high quality lense, no shake ) you'll probably be able to pull off a decent crop off a photo - but not something as small as a bird. You wouldn't get the detail you desire with that.

11-14-2004, 09:20 PM
Thanks for all the replies. I tried comparing the stanford test shot of the building with the stained glass here on this site between the A85 and the G6. Lucky for me, the shot seems to have been done almost at the same time because the clouds are in the same form. most of the time the shot is done at slightly different distances or zoom and it's difficult to get a direct comparison of detail between different cameras. I agree with most of what was said: it feels like a lot of mp = very little extra zoom power, but it does work. It feels like I got maybe around 40mm zoom out of the 3 extra mp's on the g6, maybe less.

Wayne Knight
11-18-2004, 03:29 AM
A high megapixel is not an effective zoom replacement, but here's the maths to show why.

Let's say you have a 5 megapixel camera.

If you wanted to zoom the image in by 2x, then you would be dividing the number of effective pixels by 4, hence you'd end up with a 1.25 megapixel camera. If you wanted to zoom in by 3x, then you would be dividing the number of effective pixels by 9, hence you'd end up with a 0.56 megapixel image.

So you see, even if you want a 3x zoom, you're dividing the pixel count by nine.

I mean, a high number of pixels is good for reasonable cropping, but not for any serious zooming where you go right into a certain part of the image.